Flameholder



Dec. 29, 1959 R. c. HURD FLAMEHOLDER Filed Sept. 21, 1955 mvE/v ran RICHARD 0. H090 United States Patent FLAMEHOLDER Richard C. Hurd, Manchester, Conn., assignor to United Aircraft Corporation, East Hartford, Conn., a corporation of Delaware Application September 21, 1955, Serial No. 535,603

12 Claims. (Cl. 6039.72)

This invention relates to a flameholder apparatus and, more particularly, to the type used for example in afterburners for jet engines or in other combustion chambers.

The flameholder functions to create enough turbulence in the combustible mixture of gas flowing through the combustion chamberin which the flameholder is located to cause the combustiblemixture to burn within the combustion chamber without having the flame blown downstream or out by the normal velocity of the gases through the chamber.

An object of this invention is to provide a flameholder which will properly hold the flame within the combustion chamber and which will prevent blowout at theoperating velocities of gas flow which pass through the combustion chamber.

Another object of this invention is to provide a shrouded flameholder which will provide a proper region of low relative velocity of sufficient size to establish a flame.

A further object of this invention is to provide a flameholder which will have a low pressure loss therethrough during nonafter-burning.

Another object of this invention is to provide a flameholder having a minimum of actuating mechanism and moving parts necessary for its operation.

A further object of this invention is to provide aflameholder having means for directing a cooling flow of--air along the inner boundary thereof.

Other objects and advantages will be apparent from the specification .and claims and from theaccompanying drawings which illustrate embodiments of the invention.

Fig. .1 :is a view of a jet engine and afterburner combination with the greater portion of the enginein outline form and with the remainder of theengine and the afterburner in cross section.

Fig. 2 is an enlarged view, in section, of the upper part of the flameholder shown in Fig. 1. I

Fig. 3 is an enlarged view of a modification of a flameholder adapted for use in an afterburner such as shown in Fig. 1.

Fig. 4 is a front view of Fig. 3 showing a portion of the circumference of the flameholder.

With reference to Fig. 1, the turbojet engine 2 shown is a centrifugal type having its compressor 7 driven by turbine 4. Combustion chambers 5 therein deliver air from the compressor to the turbine. An afterburner 6 is attached to the turbine outlet to provide a means for increasing the thrust of .the engine.

Air is directed into the engine to the compressor. Compressed air discharging from the compressor passes to the turbine 4 through the combustion chambers where it is mixed with fuel and where the mixture burns. Fuel is delivered to said engine through conduit 8. The fuelair mixture is initially ignited within the combustioncham- From the turbine 4, the gases. pass around .a tail cone 2,918,794 Patented Dec. 29, 1959 12 into the diffuser section 14 of the afterburner. When the afterburner is operating, fuel is discharged into these gases from a plurality of fuel nozzles 16, connected to fuel conduit 17 and located in diffuser 14. Since the gases leaving the turbine 4 contain considerable unburned oxygen, the additional fuel introduced by fuel nozzles 16 provides a combustible mixture which may be initially ignited within the combustion chamber 18 by a spark igniter 20. Here again, for the afterburner, it is to be understood that any suitable type of fuel supply means and ignition means for an afterburner can be used. The burning of this combustible mixture is stabilized in the combustion chamber 18 of the afterburner by a flameholder 22. A flameholder accomplishes this by providing an area in which the velocities are maintained at a value below that at which blowout occurs. The burned gases discharge from the engine through the nozzle 24 whose area can be varied.

The variable nozzle 24 operates between a minimum opening for engine operation without afterburning and a maximum opening for operation of the engine with afterburning. The nozzle actuating system as shown comprises a cylinder 26 with a piston 28, a nozzle control rod 30 and .a piston rod 32. The variable nozzle 24 is opened or closed by admitting an actuating pressure to one side or the other of piston '28 through conduits 34 or 36. Several of these actuating systems may be used around the periphery of the nozzle 24. It can be seen that if a pressure is admitted through conduit 34 to the right side of the several pistons 28, and the left side of each piston 23 is vented, the nozzle 24 will be moved in a nozzle opening manner. If an operating pressure is admitted through conduit 36 to the left side of pistons 28, and the right side of these pistons are vented, the nozzle 24 will be moved in a closing direction. While the selection and admission of this actuating pressure and venting can be performed manually, a nozzle control which-will perform such function automatically is shown and claimed in US. Patent No. 2,715,311.

With reference to Fig. 2, the fla-meholder 22 has an annular perforated member 40, of V-shaped cross section, fixedly mountedin an annular shroud 42. The annular shroud 42 includes a double-walled inner annular -.member 50 mounted within double-walled outer annular in position and providing the proper spacing therebetween.

This proper spacing of these members provides an annular inlet 54 into said shroud, and an annular outlet 60. While the flameholder is described as being formed of annular members, these members may be formed of other shapes such as, for example, flat-sided or oval.

The outer walls 62 and 64 of the inner and outer annular members 50 and 52, respectively, of the annular shroud 42, form a substantially streamlined body from the leading edges 66 and 68 thereof to the trailing edges 70 and 72. The forward portions of the outer walls of the annular shroud diverge from the leading edges 66, 68 to a point located near the center of the annular shroud and the rearward portions converge substantially therefrom to the trailing edges 70, 72. The contour of the outer wall '62 and the outer wall 64 form, at any one section taken through the shroud, part of an airfoil section with the center line A (see Fig. 2).

The inner walls 74 and 76 of the inner and outer annular members 50 and 52, respectively, of the annular shroud 42 form a chamber 55 having a diverging forward portion 56 and a converging rearward portion 58. The diverging portions of the inner wall 74 and 76 are, at any longitudinal section taken through the shroud, straight lines and each line forms with the center line A (see Fig. 2) an-angle B.

The converging portion 58 of the chamber has the inner walls of the members 50 and 52 positioned adjacent to outer walls 62 and 64. Annular member 52 has a closed chamber 88 formed in the forward end thereof between the forward conical annular portion of the inner wall 76 and the forward portion of the outer wall 64. Annular member 50 has a closed chamber 90 formed in the forward portion thereof between the forward flat annular portion of the inner wall 74 and the forward portion of the outer wall 62. These walls 62 and 74 are connected together at their leading edges, as shown. To cool the surface area adjacent to the perforated member 40, holes 92 are provided in the leading edges of member 50 and 52 to admit fluid to the chambers 88 and 90 and holes 94 are provided in the walls 74 and 76 to direct the fluid from the chambers onto the adjacent surfaces. Support members 200 may be inserted in the chambers 88 and 90 for reinforcing. It will be apparent that these chambers extend rearwardly at least as far as the rows of holes 94.

The annular shroud 42 is fixedly mounted within the afterburner 6 by radially extending strut members 44, Fig. l. Annular perforated member 40 is mounted within the shroud 42 by having its leading edge 80, formed by the V, fixed to the strut members 46. Member 40 is positioned approximately at the widest section of the chamber 55 to be in an area of reduced velocity in order to stabilize combustion. The trailing edges of the member 40 are spaced from the sides of the chamber 55. Strut members 44 and 46 are fixed in position by any suitable means.

As stated hereinbefore, fuel nozzles 16 introduce fuel into the gases leaving the turbine 4 which gases contain a considerable amount of unburned oxygen. This pro vides a combustible mixture. To insure that this combustible mixture will be thoroughly mixed and properly brought in to contact with the fiame leaving the outlet 60 of the fiameholder, vortex generators 100 are provided around the outer wall 64 of the outer annular member 52 to project radially outwardly of the afterburner axis and other vortex generators around the outer wall 62 of the inner annular member 50 project radially inwardly toward the afterburner axis. These vortex generators produce turbulence as the mixture flows over the flameholder and approaches the outlet 60.

With reference to Fig. 3, the fiameholder 22 is shown having a variable area outlet 60 and also with retractable turbulence promoters 102 mounted in recesses 104. These recesses 104 are formed in the forward portion of the outer walls 62 and 64 of the inner and outer annular members 50 and 52.

The variable area outlet 60' is formed by having the rear portion of the annular members 50 and 52 slotted as at 106 to form a plurality of flap members 108. These flap members 108 are formed as bimetallic elements responsive to temperature. The rear section of the fiameholder formed of the bimetal parts is fixed to the remainder of the fiameholder at 150. As the temperature increases, the turbulence promoters 102 move about their forward ends and project into the gas stream as shown by the dotted lines, and as the temperature increases the flap members 108 move about their forward ends outwardly to a position represented by the dotted lines (see Fig. 3).

When the afterburner is off, the fiameholder is in the position shown by the solid lines in Fig. 3. When the afterburner is turned on, thus increasing the temperature within the afterburner, the flap members 108 move from the fiameholder an amount depending on the temperature therearound. Turbulence promoters 102 are hinged at their forward end and may be operated by any means desired. An example of a flap operating mechanism is shown in Fig. 4 of the patent to Browning, US. Patent No. 2,496,083.

Although only two modifications have been shown and described herein for purposes of illustration, it will be evident to those skilled in the art that the invention is capable of various modifications and adaptations within the scope of the appended claims.

I claim:

1. In combination, a combustion chamber through which gases pass at high velocities, a fiameholder mounted in said chamber, said fiameholder including a shroud member, said shroud member comprising an inner and outer member, said inner and outer members being spaced from each other by struts extending between said members to provide an inlet, a diffusing section and an outlet, and a perforated member of V-shape cross section having its leading edge fixed to said struts, said perforated member being located in said diffusing section.

2. In combination, a combustion chamber through which gases pass at high velocities, a fiameholder mounted in said chamber, said fiameholder including a shroud member, said shroud member having an inlet, a diverging section and an outlet, and a perforated member being mounted adjacent the end of the diverging section of said shroud, said outlet being formed as flaps, said flaps being movable in response to temperature.

3. In combination, a combustion chamber through which gases pass at high velocities, a fiameholder mounted in said chamber, said fiameholder including a shroud member, said shroud member having an inlet, a diverging section and an outlet, a perforated member being mounted adjacent the end of the diverging section of said shroud, and a plurality of flaps being mounted around the inlet of said shroud member, each flap being movable from a position faired with said shroud member to a position where its trailing edge projects from the shroud member.

4. In combination, a combustion chamber through which gases pass at high velocities, a fiameholder mounted in said chamber, said fiameholder including inner and outer shroud members, said shroud members being radially spaced part to define between them an inlet, a diverging section and an outlet, and a perforated memher being mounted between the shrouds and adjacent the end of the diverging section of said shroud, at least one of said shroud members being hollow, and means for directing a fluid through said hollow shroud from a point near the inlet of said shroud member to a point adjacent the perforated member.

5. In combination, a combustion chamber through which gases pass at high velocities, a fiameholder mounted in said chamber, said fiameholder including a shroud member, said shroud member comprising an inner and outer member, said inner and outer members being spaced from each other by struts extending between said members, each inner and outer member having an inner and outer surface, said spacing of said inner and outer members placing the inner surface of the outer member opposite the inner surface of the inner member forming an inlet, a diverging section and an outlet, and a perforated member being fixed to said struts between the inner and outer members and spaced from at least one of said members.

6. In combination, a combination chamber through which gases pass at high velocities, a ring-like fiameholder mounted in said chamber, said fiameholder including a shroud member, said shroud member comprising an inner and outer member, said inner and outer members being spaced from each other by struts, each inner and outer member having an inner and outer surface, said spacing of said inner and outer members placing the inner surface of the outer member opposite the inner surface of the inner member forming an inlet, a diverging section and an outlet, and a perforated member being fixed to said struts between the inner and outer members and spaced from at least one of said members, said perforated member being located adjacent said diverging section.

7. In combination, a combustion chamber through which gases pass at high velocities, an annular flameholder mounted in said chamber, said flameholder including inner and outer annular shroud members, said inner and outer members being radially spaced from each other, struts extending between and supporting said members, each inner and outer member having an inner and outer surface, said spacing of said inner and outer members placing the inner surface of the outer member op posite the outer surface of the inner member and in spaced relation thereto, said members forming between them a passage having an inlet, a diverging section and an outlet, and a perforated member of V-shape cross section having its leading edge fixed to said struts, said perforated member being located in said diverging section.

8. In combination, a combustion chamber through which gases pass at high velocities, an annular flameholder mounted in said chamber, said flameholder including inner and outer annular shroud members, said inner and outer members being radially spaced from each other, struts extending between and supporting said members, each inner and outer member having an inner and outer surface, said spacing of said inner and outer members placing the inner surface of the outer member opposite the outer surface of the inner member and in spaced relation thereto forming an inlet, a diverging section and an outlet, and a perforated member between said members and fixed to said struts, and vortex generators mounted on the outer surface of said outer member adjacent to the periphery of said perforated member.

9. In combination, a combustion chamber through which gases pass at high velocities, a flameholder mounted in said chamber, said flameholder including a shroud member, said shroud member comprising an inner and outer member, said inner and outer members being spaced from each other by struts, each inner and outer member having an inner and outer surface, said spacing of said inner and outer members placing the inner surface of the outer member opposite the inner surface of the inner member forming an inlet, a diverging section and an outlet, a perforated member being fixed to said struts, and a plurality of flaps mounted around said outlet.

10. In combination, a combustion chamber through which gases pass at high velocities, a flameholder mounted in said chamber, said flameholder including a shroud member, said shroud member comprising an inner and outer member, said inner and outer members being spaced from each other by struts, each inner and outer member having an inner and outer surface, said spacing of said inner and outer members placing the inner surface of the outer member opposite the inner surface of i the inner member forming an inlet, a diverging section and an outlet, and a perforated member being fixed to said struts, said outlet being formed of flap-like members, said outer surface of said outer member having vortex generators mounted therearound.

11. In combination, a combustion chamber through which gases pass at high velocities, a flameholder mounted in said chamber, said flameholder including a shroud member, said shroud member comprising an inner and outer member, said inner and outer members being spaced from each other by struts, each inner and outer member having an inner and outer surface, said spacing of said inner and outer members placing the inner surface of the outer member opposite the inner surface of the inner member forming an inlet, a diverging section and an outlet, and a perforated member being fixed to said struts, said outlet being formed of flap-like members, said outer surface of said outer member having vortex generators mounted therearound, said outer surface of said inner member having vortex generators mounted therearound.

12. In combination, a combustion chamber through which gases pass at high velocities, a flameholder mounted in said chamber, said flameholder including a shroud member, said shroud member comprising an inner and outer member, said inner and outer members being spaced from each other by struts, each inner and outer member having an inner and outer surface, said spacing of said inner and outer members placing the inner surface of the outer member opposite the inner surface of the inner member forming an inlet, a diverging section References Cited in the file of this patent UNITED STATES PATENTS 2,558,816 Bruynes July 3, 1951 2,603,949 Brown July 22, 1952 2,679,137 Probert May 25, 1954 FOREIGN PATENTS 1,090,450 France Oct. 20, 1954 UNITED STATES PATENT OFFICE CERTIFICATE 0F CORRECTION Patent No, 2,918,794 December 29, 1959 Richard C. Hurd It is hereb$ certified that error appears in the-printed specification of the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

Column 4, line 38, for "part read apart line 60, for "combination", second occurrence, read 1 combustion Signed and sealed this 28th day of June 1960.,

(SEAL) Attest:

KARL H. AXLINE ROBERT C. WATSON Attesting Officer Commissioner of Patents 

